In order to perform fine control of motion of an actuator or the like, high-resolution positioning precision is required. In order to carry out high-resolution control of position, it is necessary to equip feedback control with a high-resolution encoder which detects the rotational angular position of a motor. There are many high-resolution encoders that transmit data by serial communication. Owing to serial communication (serial data), a problem which arises is that communication takes time (tens of microseconds, for example).
Patent Document 1 describes a feedback control method and apparatus for a stepping motor serving as an example of motor control. In the control apparatus, the output of a single encoder is used as a feedback signal for controlling the position and velocity of a stepping motor. In a case where use is made of an encoder that transmits data at a high resolution by means of serial communication, even though tens of microseconds are required on account of serial communication, in control of position no particularly significant problem arises because it will suffice if feedback control is carried out at a control cycle on the order of milliseconds.